High-barrier polyethylene terephthalate film

ABSTRACT

A high-barrier film is provided that includes a biaxially-oriented polyethylene terephthalate (PET) layer having a first side and a second side opposite the first side, a cross-linked acrylic primer layer, and a metal barrier layer. The cross-linked acrylic primer layer is adjacent to the second side of the PET layer and has a dynamic coefficient of friction (μD) to steel of less than about 0.45, while the metal barrier layer is adjacent to the first side of the PET layer. The film has a total thickness of less than or equal to about 12 μm. Processes for producing the high-barrier film are also provided.

RELATED APPLICATIONS

This application is a Continuation-In-Part application of U.S.application Ser. No. 14/193,950, filed Feb. 28, 2014, which claimspriority from U.S. Provisional Application Ser. No. 61/840,290, filedJun. 27, 2013, the entire disclosures of which are incorporated hereinby this reference.

TECHNICAL FIELD

The presently-disclosed subject matter relates to high-barrierpolyethylene terephthalate films and processes for producing the same.In particular, the presently-disclosed subject matter relates tohigh-barrier polyethylene terephthalate films having abiaxially-oriented polyethylene terephthalate layer, a cross-linkedacrylic primer layer, and a metal barrier layer.

BACKGROUND

It is appreciated that the density of the amorphous phase withinbiaxially-oriented polyethylene terephthalate (PET) film is directlyrelated to the overall gas barrier properties. It is also appreciatedthat the amorphous content of any PET film is the weight fraction ofmaterial that is not crystallized within the biaxial orientationprocess, and that the densification of the amorphous phase implies thatthe mass per unit volume of non-crystalline material is increased (see,e.g., Polymer Bulletin, April 1988, Volume 19, Issue 4, pp. 397-401,which is incorporated herein by this reference in its entirety). In thisregard, crystallinity and amorphous phase densification are bothparameters that can be modified on a conventional biaxially-orientedstretching machine through stretch ratio conditions, the temperature ofstretching, and the subsequent heat-setting of the film. Moreover, suchdensification is known to increase with the orientation of PET film.

In producing high-barrier PET films, however, although the use of analuminum vacuum deposition process to produce a barrier layer in thefilm is common, the use of such a process does not guarantee thesuitability of the resulting films for very high-barrier requirementsdue to the potential for defects. Indeed, defect population and type ofdefect become limiting factors for very high-barrier applications makinguse of vacuum-deposited metal surfaces, such as what may be found in thehigh-barrier films that are often necessary for extending shelf-life infood and electronics packaging, tobacco, medical packaging, and otherindustrial uses such as the fabrication of balloons.

Vacuum metallizing thin films at the high optical densities, oftengreater than 2.7 OD, needed for very high gas barrier applications canresult in thermal distortions to the films during the process. Indeed,it is typical for these distortion problems to result in heat lanes ortracks or, in other words, areas of localized shrinkage within the PETfilm structure that are due to a high heat load that is not dissipatedquickly. Metal adhesion, barrier properties, and appearance are then allpoor within the film areas that heat lanes develop.

In order to combat the defects caused by heat lanes, it is common to usea gas wedge in the vacuum metallizing process. This process consists ofinjecting a gas between the moving PET web and the chill roll in thevacuum metallizing process. The increased thermal transfer from chillroll to film is often enough to reduce heat lanes in metallized films toan acceptable level. However, in the case of very thin films (less thanabout 10 μm), the ability of the film to traverse the chill rollassembly without sticking, wrinkling, or distorting is a serious issue.Additionally, in such situations, the use of high tensions on the thinfilm to keep the film flat on the chill roll is practically impossibledue to the tensile limitations of the film under a heat load. Onesolution to this problem is to run the film at reduced speeds in themetallizing chamber. However, the significant commercial cost of runningfilm at reduced speeds makes that approach unrealistic.

Accordingly, there remains a need in the art to produce a thin,high-barrier, and high-adhesion PET film at commercially-acceptable linespeeds. Such films and processes are particularly desirable andbeneficial for a range of applications in food and consumer packagingand in the fabrication of industrial commodities.

SUMMARY

The presently-disclosed subject matter meets some or all of theabove-identified needs, as will become evident to those of ordinaryskill in the art after a study of information provided in this document.

This summary describes several embodiments of the presently-disclosedsubject matter, and in many cases lists variations and permutations ofthese embodiments. This summary is merely exemplary of the numerous andvaried embodiments. Mention of one or more representative features of agiven embodiment is likewise exemplary. Such an embodiment can typicallyexist with or without the feature(s) mentioned; likewise, those featurescan be applied to other embodiments of the presently-disclosed subjectmatter, whether listed in this summary or not. To avoid excessiverepetition, this summary does not list or suggest all possiblecombinations of such features.

The presently-disclosed subject matter includes high-barrierpolyethylene terephthalate films and processes for producing the same.In particular, the presently-disclosed subject matter includeshigh-barrier polyethylene terephthalate films having abiaxially-oriented polyethylene terephthalate layer, a cross-linkedacrylic primer layer, and a metal barrier layer.

In some embodiments of the presently-disclosed subject matter, ahigh-barrier film is provided that comprises a biaxially-orientedpolyethylene terephthalate (PET) layer having a first side and a secondside opposite the first side, a cross-linked acrylic primer layer thatis adjacent to the second side of the PET layer and that has a dynamiccoefficient of friction (μD) to steel of less than about 0.45, and ametal barrier layer that is adjacent to the first side of the PET layer.In some embodiments, such a film has a total thickness of less than orequal to about 12 μm, and a tensile strength of at least about 2500kg/cm² in both a transverse direction and a longitudinal direction ofthe film. In some embodiments, such a film has a total thickness of lessthan or equal to about 12 μm, and a surface roughness of less than about5 nm. In some embodiments, such a film has a total thickness of lessthan or equal to about 12 μm, and an oxygen (O₂) transmission rate ofless than about 1.0 cc/m²/day. In some embodiments, the film has anoptical density of greater than about 2.7.

With respect to the cross-linked acrylic primer layer included in thehigh-barrier films, in some embodiments, the cross-linked acrylic primerlayer comprises an acrylate selected from the group consisting ofmethylmethacrylate, butylacrylate, methacrylic acid, methyl acrylate,acrylic acid, and hydroxyethylmethacrylate, and combinations thereof. Toproduce a sufficiently hard acrylic primer layer, the acrylic primerlayer can further include a cross-linking agent selected from the groupconsisting of melamines, dicyclocarbodiimides, epoxies, and aldehydes.In this regard, in some embodiments, the cross-linked acrylic primerlayer has a cross-linking density of about 10% to about 40%. In someembodiments, the cross-linked acrylic primer layer has a dynamiccoefficient of friction (μD) to steel of less than about 0.45 or lessthan about 0.20 when heated to 150° C. Such cross-linked acrylic primerlayers can have a thickness of less than about 0.3 μm, less than about0.15 μm, or less than about 0.05 μm.

The metal barrier layers of the presently-described films are typicallycomprised of either aluminum or aluminum oxide. In certain embodiments,the metal barrier layer is comprised of aluminum oxide to produce a filmhaving an oxygen transmission rate of less than about 1.5 cc/day/m². Insome embodiments, a high-barrier film has an amount of adhesion of themetal barrier layer to the PET layer of greater than about 150 g/inch.

Further provided by the presently-disclosed subject matter are processesfor producing a high-barrier film. In some embodiments, a process forproducing a high-barrier film is provided wherein a biaxially-orientedPET layer having a first side and a second side opposite the first sideis first produced by melting an amount of PET pellets to form an initialPET layer. That initial PET layer is then stretched in a longitudinaldirection, and a second side of the PET layer is subsequently in-linecoated with a cross-linked acrylic primer to produce a cross-linkedacrylic primer layer having a dynamic coefficient of friction (μD) tosteel of less than about 0.45. After coating the second side of the PETlayer with the cross-linked acrylic primer, the PET layer is thenstretched in a transverse direction. To complete the film, the firstside of the PET layer is then corona treated and vacuum metallized toproduce a film having a desired optical density. In some embodiments,the film is vacuum metallized to an optical density of greater thanabout 2.7.

Further features and advantages of the presently-disclosed subjectmatter will become evident to those of ordinary skill in the art after astudy of the description, figures, and non-limiting examples in thisdocument.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary high-barrier PET film madein accordance with the presently-disclosed subject matter.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The details of one or more embodiments of the presently-disclosedsubject matter are set forth in this document. Modifications toembodiments described in this document, and other embodiments, will beevident to those of ordinary skill in the art after a study of theinformation provided in this document. The information provided in thisdocument, and particularly the specific details of the describedexemplary embodiments, is provided primarily for clearness ofunderstanding and no unnecessary limitations are to be understoodtherefrom. In case of conflict, the specification of this document,including definitions, will control.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the presently-disclosed subject matter belongs.Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresently-disclosed subject matter, representative methods, devices, andmaterials are now described.

Following long-standing patent law convention, the terms “a,” “an,” and“the” refer to “one or more” when used in this application, includingthe claims. Moreover, unless otherwise indicated, all numbers expressingquantities of ingredients, properties such as reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thisspecification and claims are approximations that can vary depending uponthe desired properties sought to be obtained by the presently-disclosedsubject matter.

As used herein, the term “about,” when referring to a value or to anamount of mass, weight, time, volume, concentration or percentage ismeant to encompass variations of in some embodiments ±20%, in someembodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, insome embodiments ±0.5%, and in some embodiments ±0.1% from the specifiedamount, as such variations are appropriate to perform the disclosedmethod. Additionally, as used herein, ranges can be expressed as from“about” one particular value, and/or to “about” another particularvalue. It is also understood that there are a number of values disclosedherein, and that each value is also herein disclosed as “about” thatparticular value in addition to the value itself. For example, if thevalue “10” is disclosed, then “about 10” is also disclosed. It is alsounderstood that each unit between two particular units are alsodisclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and14 are also disclosed.

The presently-disclosed subject matter includes high-barrierpolyethylene terephthalate films and processes for producing the same.In particular, the presently-disclosed subject matter includeshigh-barrier polyethylene terephthalate films having abiaxially-oriented polyethylene terephthalate layer, a cross-linkedacrylic primer layer, and a metal barrier layer.

As shown in FIG. 1, in some embodiments of the presently-disclosedsubject matter, a high-barrier film is provided that comprises abiaxially-oriented polyethylene terephthalate (PET) layer having a firstside and a second side opposite the first side; a cross-linked acrylicprimer layer positioned adjacent to the second side of the PET layer andhaving a dynamic coefficient of friction (μD) of less than about 0.45;and a metal barrier layer positioned adjacent to first side of thecross-linked acrylic primer layer. In some embodiments, the totalthickness of the film having the foregoing layers is less than or equalto about 12 μm.

The PET layers included in the high-barrier films can comprise PEThomopolymers, where the PET layer consists of only PET, or can comprisePET copolymers, where the PET layer includes PET and one or moreadditional co-monomers. Additional co-monomers that can be used in thisregard include diethylene glycol, propylene glycol, neopentyl glycol andpolyalkylene glycols, 1,4-butane diol, 1,3-propane diol, anddicarboxylic acids such as adipic acid, sebacic acid, malonic acid,succinic acid, isophthalic acid, and 2,6-napthalenedicarboxylic acid.

Regardless of whether the PET layer includes PET homopolymers orcopolymers, the PET layer included in the films of thepresently-disclosed subject matter is generally prepared by processesknown to those of ordinary skill in the art including the use ofconventional sequential biaxial orientation machines having a singlescrew mainline extrusion train and a twin screw sub-extrusion process.In this regard, in some embodiments, standard PET pellets having adesired intrinsic viscosity can be fed into the main extrusion line,while a blend of standard PET pellets and silica-filled PET pellets canbe fed in to the sub-extrusion process, such that the materials can bemelted separately and then laminated together in a feed-block to producea desired molten structure (e.g., an A/B/A molten structure) in anextrusion die. The laminated PET material or layer emerging from theextrusion die can then quenched on a chilled casting drum to produce athick, amorphous film structure. The PET layer is then preferablystretched about 2 to about 5 times in the machine, or longitudinal,direction and, after the acrylic primer coating process described below,about 2 to about 5 times in the transverse direction, followed by heatcrystallization. In some embodiments, after stretching the PET layer inthe longitudinal and transverse direction and crystallization, a layerof PET material is obtained having a tensile strength of at least about2500 kg/cm² in both the transverse and the longitudinal direction of thefilm, and having dimensions that are about 3.4 times those originallyfound in the PET layer in both the longitudinal and transversedirection. In some embodiments, the resulting PET layer has a totalthickness of about 6 μm to about 12 μm, including, in some embodiments,PET layers having a total thickness of about 6 μm, about 7 μm, about 8μm, about 9 μm, about 10 μm, about 11 μm, and about 12 μm.

With respect to the acrylic primer layer included in the high-barrierfilms of the presently-disclosed subject matter, the acrylic primerlayer is highly cross-linked and capable of providing a low coefficientof friction (COF) to metal to increase the contact of film to metal andto facilitate the vacuum metallizing process described below. In someembodiments, the dynamic COF of the acrylic layer of the film to themetal is about 0.15 μD to about 0.45 μD when heated to 150° C. In someembodiments, the dynamic COF of the acrylic layer of the film to themetal is about 0.15 μD, about 0.20 μD, about 0.25 μD, about 0.30 μD,about 0.35 μD, about 0.40 μD, or about 0.45 μD. In some embodiments, thedynamic COF of the acrylic layer of the film to the metal is less thanabout 0.45 μD when heated to 150° C. In some embodiments, the COF of theacrylic layer of the film to the metal is less than about 0.20 μD whenheated to 150° C.

In some embodiments, to produce an acrylic primer layer having suchproperties, the acrylic primer layer can be comprised of an acrylicresin that adheres well to the PET layer. Such acrylic resins can beselected from resins having a monomer component such as, for example, analkyl acrylate, an alkyl methacrylate, (examples of such alkyl groupsinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, a t-butyl group, a2-ethylhexyl group, a lauryl group, a stearyl group, a cyclohexyl group,a phenyl group, a benzyl group, a phenylethyl group and the like), amonomer having a hydroxyl group such as 2-hydroxyethyl acrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropylmethacrylate or the like, a monomer having an amide group such asacrylamide, methacrylamide, N-methyl acrylamide, N-methylmethacrylamide, N-methylol acrylamide, N-methylol methacrylamide,N,N-dimethylol acrylamide, N-methoxymethyl acrylamide,N-methoxymethylmethacrylamide, N-phenyl acrylamide or the like, amonomer having an amino group such as N,N-diethylamino ethyl acrylate,N,N-diethylamino ethyl methacrylate or the like, a monomer having anepoxy group such as glycidyl acrylate, glycidyl methacrylate or thelike, a monomer having a carboxylic acid or a salt thereof such asacrylic acid, methacrylic acid or a salt thereof (an alkali metal salt,an alkali earth metal salt, an ammonium salt or the like) and the likewhereupon one or more types of such monomer components arecopolymerized. In some embodiments, the acrylic primer is comprised of acopolymer of methyl methacrylate that further includes methacrylic acidand methacrylonitrile. In some embodiments, the acrylic primer iscomprised of a co-polymer of methylmethacrylate, butylacrylate,methacrylic acid, methyl acrylate, acrylic acid, andhydroxyethylmethacrylate, alone or in combination with other monomers,as such a combination of monomers has been observed to produce anacrylic primer layer having sufficient hardness and COF values as wellas a sufficient ability to adhere to down-stream sealants including, butnot limited to, polyethylene, ethylene vinyl acetate, ethylene methylacrylate, and copolymers and terpolymers thereof.

In addition to the acrylic components of the acrylic primer layer, oneor more cross-linking agents are typically also included in the acrylicprimer layer to harden the acrylic primer layer, to reinforce thebonding between the various layers of the high-barrier film, and to alsoprovide a highly cross-linked layer capable of providing increasedthermal resistance when the film is subsequently vacuum-metallized.Exemplary cross-linking agents that can be used with the acryliccomponents include, but are not limited to, melamine-basedcross-linkers, epoxy-based cross-linkers, aziridine-based cross-linkers,epoxyamide compounds, titanate-based coupling agents (e.g., titaniumchelate), oxazoline-based cross-linkers, isocyanate-based cross-linkers,methylolurea or alkylolurea-based cross-linkers, aldehyde-basedcross-linkers, and acrylamide-based cross-linkers. In some embodiments,the cross-linking agent is selected from melamine, epoxy-basedcross-linkers, and aldehyde-based cross-linkers.

In some embodiments, the cross-linking agents are included in theacrylic primer layer to produce a cross-linked acrylic primer layerhaving a cross-linking density of about 10%, about 15%, about 20%, about25%, about 30%, or about 40%. In some embodiments, the cross-linkingagents are included in the acrylic primer layer to produce across-linked acrylic primer layer having a cross-linking density ofgreater than about 10%.

The acrylic primer layer can be applied to the second side of the PETlayer by a number of methods, including application of the acrylicprimer in a dispersion or solution of water, and by an applicationmethod such as gravure coating, meyer rod coating, slot die, knife overroll, or any variation of roll coating. In one preferred embodiment, theacrylic primer layer is applied by inline coating, whereby the acrylicprimer layer is applied to the PET layer as it is being produced. Morespecifically, and as described above, the acrylic primer layer ispreferably applied to the second side of the PET layer by inline coatingimmediately after stretching the PET layer in the longitudinaldirection. In some embodiments, the thickness of the acrylic primerlayer that is applied to the second side of the PET layer is about 0.3μm, about 0.25 μm, about 0.2 μm, about 0.15 μm, about 0.10 μm, or about0.05 μm.

Once the acrylic primer layer has been applied to the PET layer, anelectrical treatment, such as a plasma or corona treatment, can then beoptionally used to change the surface energy on the first side of thePET layer and thereby allow for increased bond strength between the PETlayer and the metal barrier layer upon its deposition. In someembodiments, the layers can be corona treated to a dyne value of about50 to about 60 dynes (e.g., 56 dynes), as such dyne values have beenobserved to allow sufficient bonding between the metal barrier layer andthe PET film. Typically, the bonding strength or, in other words, thestrength of the metal adhesion to the PET film, is greater than 150 g/inand, preferably, greater than 250 g/in as measured by first laminating astrip of an ionomer resin (e.g., Surly, DuPont de Nemours and Company,Wilmington, Del.) to the deposited metal layer on the film and thenremoving the metal by pulling on the resulting film-ionomer laminate ina tensile tester according to Association of International Metallizers,Coaters, and Laminators (AIMCAL) guidelines for measuring metal adhesionto films.

Turning now to the application of the metal barrier layer, the term“metal barrier layer” is used herein to refer to both traditionalmetallized layers, such as aluminum layers, as well as more ceramic-likelayers, such as layers comprised of silicon oxide and/or aluminum oxide.Such metal barrier layers can be applied adjacent to the first side ofthe PET layer using a number of deposition methods including, but notlimited to, physical vapor deposition or chemical vapor deposition. Inone preferred embodiment, the metal barrier layer is an aluminum oxidelayer that is applied by physical vapor deposition in a vacuum in situ,where aluminum is heated under low pressure conditions (e.g., less thanabout 1.0×10⁻³ mbar) in the presence oxygen gas to allow the aluminum toform a vapor at lower temperature and then be applied to the film as aclear barrier layer of aluminum oxide without causing thermal damage tothe other layers during its application. In some embodiments, an amountof aluminum oxide is applied to the first side of the PET sufficient toprovide an oxygen transmission rate of less than 1.5 cc/m²/day In someembodiments, the oxygen transmission rate of the presently-disclosedfilms is less than about 1.0 cc/m²/day, such as, in certain embodiments,about 0.5 cc/m²/day.

In another preferred embodiment of the presently-described high-barrierfilms, the metal barrier layer can be in the form of an aluminum layerthat can be formed by heating an aluminum wire fed to the surface of anelectrically heated plate or by heating an ingot of aluminum within acrucible, and then condensing the resulting aluminum vapor on the firstside of the PET film. In this regard, in such embodiments, the films aretypically vacuum metallized to an optical density of greater than about2.7 to provide a film capable of providing a high gas barrier. However,regardless of the particular type of metal barrier layer that isapplied, by including the acrylic primer layer having a low COF tometal, the acrylic layer allows the film to continually be in sufficientcontact with a chill roll to ensure that no thermal defects are includedon the film as the high-barrier metal layer is produced.

As a further refinement to the presently-described high-barrier films,in some embodiments, a high-barrier film is provided having a surfaceroughness, Sra, (i.e., a roughness of the surface to which themetallized layer is applied) of less than about 5 nm including, in someembodiments, less than about 4.5 nm, less than about 4.0 nm, less thanabout 3.5 nm, less than about 3.0 nm, less than about 2.5 nm, less thanabout 2.0 nm, less than about 1.5 nm, and less than about 1.0 nm.Measurement of such surface roughness (Sra) values can be made by usingany number of surface metrology methods known to those skilled in theart, including, but not limited to, the use of laser profiling andneedle stylus methods.

The presently-disclosed subject matter is further illustrated by thefollowing specific but non-limiting examples.

EXAMPLES Example 1 High-Barrier, Acrylic-Coated, Metallized PolyethyleneTerephthalate (PET) Film

PET film was prepared in a conventional sequential biaxial orientationmachine. The machine consisted of a single screw mainline extrusiontrain and a twin screw sub extrusion process. Briefly, PET pellets of anintrinsic viscosity (IV) of 0.62 were fed into the main extrusion trainat a rate of 650 Kg/hr. Into the sub-extrusion process, a blend of 0.62IV PET pellets (75%) and silica filled PET pellets (25%) were fed intothe system. The amount of silica used was optimized to produce a COF ofless than 0.45 μD at the end of the film making process. These materialswere then separately melted and laminated together in a feed-block toproduce an A/B/A molten structure in the extrusion die.

The molten laminated PET material that emerged from the extrusion diewas subsequently quenched on a chilled casting drum to produce a thick,amorphous film structure. Subsequently, this film was stretched in themachine, or lengthwise, direction through a heated roller assembly. Theratio of this stretching was varied. After longitudinal stretching, thefilm was coated with a low COF acrylic coating, and was then stretchedin the transverse direction to obtain a sheet having a dimension roughly3.4 times the original dimension of the film in both the longitudinaland transverse direction. The crystallizing temperatures were set toproduce a film with a minimum tensile strength of 2500 kg/cm² in boththe machine direction and transverse direction. The reverse side of thisfilm was then corona treated in a film making machine to a dyne value of56 dynes.

Subsequently, this film was vacuum metallized with aluminum to an OD of2.8. In this process, the low COF acrylic coating was noted to allow thefilm to lay flat on the chill roll, and the film subsequently produced(see, e.g., FIG. 1) had no heat lanes or other thermal related defects.

Example 2 Metallized Polyethylene Terephthalate (PET) Film

A second 9 μm PET film was prepared as described above in Example 1.However, in the second film, the film was stretched in the machinedirection only by a factor of 3.0. Additionally, the second film was notcoated and was side-ways drawn and heat-set to produce a film withtensile properties of roughly 2000 kg/cm² in both the longitudinal andtransverse directions. Subsequent to stretching, the second film wasvacuum metallized to an OD of 2.8 and, in that process, a small amountof heat-lanes were noted.

Example 3 Comparison of Films

To compare the acrylic-coated film from Example 1 to the uncoated,control film from Example 2, both films were processed in an additionalstep. Briefly, each film was slit into narrow rolls and were placed intoan off-line extrusion coater. In this process, each film was unwound andthe non-metal side was primed with a polyethylene primer and thenextrusion coated with a blend of polyethylene (PE) and low-densitypolyethylene (LDPE). The laminated film structures were then fabricatedinto balloon shapes. Helium was used to inflate the balloons and therelative lifetime of the balloons was measured as shown in Table 1below.

TABLE 1 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9 Example 1Firm Firm Firm Firm Firm Firm Firm Firm Firm Example 1 Firm Firm FirmFirm Firm Firm Firm Spongy Spongy Example 1 Firm Firm Firm Firm FirmFirm Firm Spongy Spongy Control 1 Firm Firm Firm Spongy Spongy SpongyDeflated Deflated Deflated Control 1 Spongy Deflated Deflated DeflatedDeflated Deflated Deflated Deflated Deflated

Lifetime was evaluated by assessing the firmness of inflated balloons.From a commercial standpoint, firmness of the balloon is believed to beimportant because when sufficient helium gas has diffused out of aparticular balloon and the shape changes and the balloon begins to feelspongy, the balloons have no or little commercial value.

As shown in Table 1, the use of the low COF acrylic-coated PET filmprovided for a much better lifetime than conventional films. Althoughnot wanting to be bound by any particular theory, it was believed thatthe low COF of the acrylic-coated films provided for more intimatecontact between the PET film and the chill roll in the vacuummetallizing chamber. Additionally, it was believed that the high tensileproperties of the acrylic-coated film allowed for higher tension in thevacuum metallizing process, which further increased the contact betweenthe chill roll and the film. Such enhanced contact between film andchill roll increased the heat transfer upon subsequent high metaldensity deposition.

Example 4 Evaluation of Additional Films

To evaluate the properties of additional acrylic-coated films, a 12 μmbiaxially-oriented PET film was produced using the methodology asdescribed above in Example 1. The 12 μm film was also coated with a lowCOF acrylic coating and was vacuum metallized. Subsequent to production,the 12 μm PET film was then compared to a 9 μm low COF acrylic-coated,vacuum metallized film produced as described in Example 1 as well as toa metallized 12 μm film having a copolyester or a copolyester/acrylichybrid coating.

As shown in Table 2, and similar to the 9 μm film, the 12 μm low COFacrylic-coated, vacuum metallized film exhibited a lower surfaceroughness (Sra) as measured by standard laser profiling techniques.Moreover, the 12 μm low COF acrylic-coated, vacuum metallized filmshowed the highest barrier results as measured by an OX-TRAN® Model 1/50according to the manufacturer's instructions (MOCON, Inc., Minneapolis,Minn.). Again, and although not wanting to be bound by any particulartheory, it was believed that the low COF of the 12 μm acrylic-coatedfilms provided for more intimate contact between the PET film and thechill roll in the vacuum metallizing chamber, which, in turn, led to anincreased smoothness of the films and a higher barrier as measured byoxygen transmission.

TABLE 2 PET Film Film to Sra- Thickness Surface Steel COF Metal SurfaceO₂ (μm) Coating (μD) OD Layer Transmission New 12 Cross-linked 0.43 2.91.4 mn 0.23 Example acrylic cc/m²/day New 12 Cross-linked 0.43 (AlOx)1.4 nm 0.50 Example acrylic cc/m²/day New 9 Cross-linked 0.43 (AlOx) 1.4nm 0.55 Example acrylic cc/m²/day Comparative 12 Copolyester 0.63 2.5526 nm 1.1 Example 1 cc/m²/day Comparative 12 Copolyester/ 0.55 2.8 17 nm0.65 Example 2 Acrylic Hybrid cc/m²/day

Throughout this document, various references are mentioned. All suchreferences are incorporated herein by reference, including thereferences set forth in the following list:

REFERENCES

1. U.S. Pat. No. 5,427,235, to Powell, et al., issued Jun. 27, 1995, andentitled “High Barrier Packages for Smoking Articles and OtherProducts.”

2. U.S. Pat. No. 6,200,511, to Peiffer, et al., issued Mar. 13, 2001,and entitled “Polyester Film Having a High Oxygen Barrier and ImprovedAdhesion to Metal Layers its Use and Process for Its Production.”

3. U.S. Pat. No. 8,236,399, to Chicarella, et al., issued Aug. 7, 2012,and entitled “Lighter than Air Balloon Made from Biaxially OrientedPolyester Film.”

4. U.S. Pat. No. 8,399,080, to Chicarella, et al., issued Mar. 19, 2013,and entitled “Lighter than Air Balloon Made from Biaxially OrientedPolyester Film.”

It will be understood that various details of the presently disclosedsubject matter can be changed without departing from the scope of thesubject matter disclosed herein. Furthermore, the foregoing descriptionis for the purpose of illustration only, and not for the purpose oflimitation.

What is claimed is:
 1. A high-barrier film, comprising: abiaxially-oriented polyethylene terephthalate (PET) layer having a firstside and a second side opposite the first side; a cross-linked acrylicprimer layer adjacent to the second side of the PET layer, thecross-linked acrylic primer layer having a dynamic coefficient offriction (μD) to steel of less than about 0.45; and a metal barrierlayer adjacent to the first side of the PET layer, wherein the film hasa total thickness of less than or equal to about 12 μm, and a tensilestrength of at least about 2500 kg/cm².
 2. The high-barrier film ofclaim 1, wherein the film has an optical density of greater than about2.7.
 3. The high-barrier film of claim 1, wherein the film has a tensilestrength of at least about 2500 kg/cm² in both a transverse directionand a longitudinal direction of the film.
 4. The high-barrier film ofclaim 1, wherein the cross-linked acrylic primer layer has across-linking density of about 10% to about 40%.
 5. The high-barrierfilm of claim 1, wherein the cross-linked acrylic primer layer has adynamic coefficient of friction (μD) to steel of less than about 0.45when heated to 150° C.
 6. The high-barrier film of claim 1, wherein thecross-linked acrylic primer layer has a dynamic coefficient of friction(μD) to steel of less than about 0.20 when heated to 150° C.
 7. Thehigh-barrier film of claim 1, wherein the cross-linked acrylic primerlayer has a thickness of less than about 0.3 μm.
 8. The high-barrierfilm of claim 1, wherein the cross-linked acrylic primer layer has athickness of less than about 0.15 μm.
 9. The high-barrier film of claim1, wherein the cross-linked acrylic primer layer has a thickness of lessthan about 0.05 μm.
 10. The high-barrier film of claim 1, wherein themetal barrier layer is comprised of aluminum or aluminum oxide.
 11. Thehigh-barrier film of claim 10, wherein the metal barrier layer iscomprised of aluminum oxide, and wherein the high-barrier film has anoxygen transmission rate of less than about 1.5 cc/day/m².
 12. Thehigh-barrier film of claim 1, wherein the high-barrier film has anamount of adhesion of the metal barrier layer to the PET layer ofgreater than about 150 g/inch.
 13. The high-barrier film of claim 1,wherein the PET layer comprises a PET homopolymer or a PET copolymer.14. The high-barrier film of claim 1, wherein the cross-linked acrylicprimer layer comprises an acrylate selected from the group consisting ofmethylmethacrylate, butylacrylate, methacrylic acid, methyl acrylate,acrylic acid, hydroxyethylmethacrylate, and combinations thereof. 15.The high-barrier film of claim 1, wherein the cross-linked acrylicprimer layer comprises a cross-linking agent selected from the groupconsisting of melamines, dicyclocarbodiimides, epoxies, and aldehydes.16. The high-barrier film of claim 1, wherein the film has a surfaceroughness of less than about 5 nm.
 17. A high-barrier film, comprising:a biaxially-oriented polyethylene terephthalate (PET) layer having afirst side and a second side opposite the first side; a cross-linkedacrylic primer layer adjacent to the second side of the PET layer, thecross-linked acrylic primer layer having a dynamic coefficient offriction (μD) to steel of less than about 0.45; and a metal barrierlayer adjacent to the first side of the PET layer, wherein the film hasa total thickness of less than or equal to about 12 μm, and a surfaceroughness of less than about 5 nm.
 18. The high-barrier film of claim17, wherein the surface roughness is about 1.5 nm.
 19. A high-barrierfilm, comprising: a biaxially-oriented polyethylene terephthalate (PET)layer having a first side and a second side opposite the first side; across-linked acrylic primer layer adjacent to the second side of the PETlayer, the cross-linked acrylic primer layer having a dynamiccoefficient of friction (μD) to steel of less than about 0.45; and ametal barrier layer adjacent to the first side of the PET layer, whereinthe film has a total thickness of less than or equal to about 12 μm, andan oxygen (O₂) transmission rate of less than about 1.0 cc/m²/day. 20.The high-barrier film of claim 19, wherein the oxygen transmission rateis less than about 0.5 cc/m²/day.
 21. The high-barrier film of claim 17,wherein the metal barrier layer is comprised of aluminum or aluminumoxide.